1. Field of the Invention
The present invention relates to a method for controlling a degaussing coil, and more particularly, relates to a method for controlling a degaussing coil of a cathode ray tube for preventing remanence of the cathode ray tube by improving operation condition of the degaussing coil, wherein the degaussing coil is installed around the cathode ray tube and eliminates residual magnetization.
2. Background of the Related Art
Generally, when a cathode ray tube is turned on, the momentary over current and over voltage causes remanence at the cathode ray tube. The remanence distorts and shakes an initial image. Consequently, a visually unstable image is output and makes a user watching a television receiver tired. Accordingly, a degaussing coil is installed around the cathode ray tube for eliminating the remanence generated during initial operation.
The degaussing coil is synchronized at the initial operation of the cathode ray tube and operates during a predetermined time. According to the operation of the degaussing coil, demagnetizing current having an opposite polar or a 180.degree.-delayed phase to the residual magnetization is generated at the cathode ray tube. The residual magnetization is canceled by the demagnetizing current generated by the degaussing coil. When the operation of the degaussing coil is stopped by the interception of the current supplied to the degaussing coil after the predetermined time, the image becomes stable.
The operation time (T) of the degaussing coil is predetermined to a similar value regardless product and conventionally, is commonly set for 3 seconds. Moreover, the cathode ray tube is turned on and the degaussing coil operates, if the cathode ray tube is turned off and then turned on within a predetermined time, that is about 30 minutes, the remanence of the cathode ray tube seems to be fully eliminated, accordingly, the degaussing coil is set not to operate any more.
In the mean time, the conventional cathode ray tube has some problems hereinafter.
If the cathode ray tube is turned on and turned off before the operation time of the degaussing coil, which is a predetermined reference operation time of the degaussing coil and, for example, is set for 3 seconds, the remanence of the degaussing coil is not fully eliminated because the degaussing coil does not properly operate for a predetermined time. And, when the cathode ray tube turns on within a predetermined time, the remanence still remains because the degaussing coil does not operate any more.